It is desired to estimate the exposure of persons to billboards which are often displayed in outdoor settings, such as along roads, highways, railways and walkways, as well as in various indoor settings, such as in malls, subway stations, railway stations, bus stations, airports, building lobbies, etc. Moreover, in addition to information concerning the numbers of persons exposed to such billboards, information concerning the days and times such exposure takes place and information concerning the particular individuals so exposed is also highly desired.
It has been proposed to employ global positioning satellite (GPS) systems to track the positions of vehicles during a period of time, and then to compare the paths of the tracked vehicles with the known locations of billboards in order to determine which billboards the tracked vehicles passed by.
This proposed technique, however, suffers from a number of disadvantages. One such disadvantage is that the technique is limited to outdoor use only due to the drastic weakening of GPS signals caused by building structures and the like. As such, the exposure to billboards displayed in indoor settings, such as in malls, subway stations, railway stations, bus stations, airports, building lobbies, etc., cannot be accurately measured using this proposed system. Another disadvantage is that the proposed GPS-based system tracks only vehicles rather than individual people. Therefore, the data collected has little or no direct correlation to the persons in the vehicle being tracked. Not only does the system not allow demographic information about the persons in the vehicle to be collected, but it does not even allow the number of persons in the vehicle to be ascertained.
Still another disadvantage is that GPS systems may be considered intrusive, in that they track the movement of people no matter where they go. Persons concerned about maintaining their privacy may be unlikely to volunteer for participation in such a billboard exposure survey.
Another system which has been proposed for measuring billboard exposure involves locating a transmitter proximate to the billboards for which exposure is to be measured and providing survey participants with portable receiving devices. The transmitters broadcast a signal that carries information related to the billboards, which signal is received and stored by the portable receiving devices.
This proposed technique, however, also suffers from a number of disadvantages. One disadvantage is that when numerous billboards are located in close proximity to one another, as is often the case in indoor settings or in high traffic outdoor settings, the signals broadcast by the transmitters associated with these billboards may conflict with one another such that the portable receiving devices cannot correctly identify at least some of the broadcast signals. As such, the estimates of exposure to at least some of the billboards may be grossly inaccurate. While techniques are available to provide a means for distinguishing among the various broadcast signals, these techniques add substantial complexity to the portable receiving devices. Since these are not mass market devices, their unit cost is substantially increased as a result.
Another disadvantage of the proposed technique relates to the fact that the data collected by the portable receivers must be subsequently downloaded by the survey participants, e.g., via a telephone line or computer link, for processing by a processing facility. This adds a further level of complexity to the system and thus still further expense.